Interferon-γ released from lymphocytes stimulated by the M. tuberculosis antigen resulted in increased platelet-derived growth factor-B (PDGF-B) in alveolar macrophages, suggesting a link between the delayed type hypersensitivity response and the first stages of a fibrotic reaction in the lungs of patients with untreated pulmonary tuberculosis [21, 22]. The gene discussed is PDGFB; the disease is pulmonary tuberculosis.